Method of and apparatus for locating water leakages into wells



G. H. ENNIS 2,184,338 METHOD OF APPARATUS FOR LOCATING WATER'LEAKAGES INTO WELLS Filed Dec. 16, v1936 3 Sheets-Sheet -1 INVENTOR 6:0265/7. f/v/v/s BY ATTORN EY 26, 1939. G. H. ENNIS 2,184,338

METHOD OF AND APPARATUS FOR LOCATING WATER LEAKAGES INTO WELLS Filed Dec. 16, 19:56 s Sheets-Sheet 2- INVENTOR fifoeai hf f/v/v/s ATTORN EY I 1939. G. H. ENNIS 2,184,338 METHOD OF. AND APPARATUS FOR LOCATING WATER LEAKAGES INTO WELLS Filed Dec. 16, 1936 3 Sheets-Sheet 3 INVENTOR 65026: /1 f/wvs ATTORNEY Patented Dec. 26, 1939.

UNITED STATES METHOD OF AND APPARATUS FOR. LOCAT- ING WATER LEAKAGES INTO WELLS George H. Ennis, Long Beach, Calm, assignor of one-half to Robert V. Funk, Long Beach,

Calif Application December 16,1936, Serial No. 116,164

17 Claims. (01. 175-183) My invention relates to the oil producing industry and particularly to a simple and improved method whereby the point of leakage of. fluid, such as water, into a well may be accurately determined.

In order that the features and advantages of my invention may be better understood I will briefly refer to the art to which my invention appertains. In the drilling of an oil well many diiferent formations are penetrated, some of which contain water, and to exclude such water from the well so that the oil when the well is placed on production will not be contaminated, one or more well casings are installed in the well and cemented in place at their lower ends. Sometimes leakages occur in the well casing or at the point cemented at the lower end thereof which results in the production of an undesirable emulsion. At other times a water sand is positioned between two producing oil sands with the result that an emulsion is formed. Also when an oil sand becomes exhausted, or nearly exhausted, water flows into the well.

It has been the practice when a well produces water to determine the point of leakage of water into the well and to then seal the wall of the well at a suitable point in order to exclude water. It is an object of this invention to provide a method whereby the point of entrance of water into a well may be located so that by a suitable cementin process the water may be excluded.

Processes in general use in the art prior to my invention all require the depositing of a special material in the,,well in order that the test may be made. This, to say the least, requires considerable time as compared to my process and is much more expensive. It is an objectof my invention to provide a method of the character pointed out in which no special material need be deposited in the well, but on'the contrary .the test is made with the fluid or material 'in the well which remains there from a previous operation whether the material in the well be a column of low gravity oil or emulsion, water, or rotary mud.

I have discoveredthat if a well which is being pumped'is allowed to stand for a period of time and that therefore the head of the column of oil or emulsion in the well is reduced to allow fluid to flow into the well from the surrounding formation, that this fluid has difierent electro-chemical characteristics which may be very small and in most instances amatter of microunits. I have found that by the use of a very sensitive recording apparatus employed in an electrical circuit and adapted to' record either microvolts or microamperes, that these very small diflferences between the fluid which has been allowed to stand in the well, and which, for the purpose of identification, I call dormant fluid, 'or dormant material, and the fluid which is allowed to flow into he well by the bailing process, and which, for the purpose of identification, I term live fluid, may be measured and in this way the point of leakage located. This diiference in electro-chemical qualities or characteristics of the live fluid may be the result of difierent causes. For example, when fluid is allowed to stand in the well any gas contained therein will tend to levitate and solid particles tend to gravitate. This results in a. dormant material of different electro-chemical characteristics than the live fluid. Also, the live fluid entering the well may be of a difierent temperature from the dormant fluid in the well, and in addition to this the fluid entering the well may cause an electromotive force 'to be set up between moving liquids and solids, both of which result in electro-chemical characteristics in the live fluid which are different from those of the dormant fluid.

In practicing my invention I may use alternative methods. For example, assuming that the well has been placed on the pump and is pumping an emulsion I remove the pumping apparatus from the well in a very careful manner so that the well fluid will not flow backwardly into the surrounding formations. I then allow the well to stand for a period of time so that the fluid will become dormant. I then by use of very sensitive apparatus test the lectro-chemical qualities'of the fluid in the well and preferably make a record thereof.. This testing apparatus may consist of an electrical circuit including two the-well form a voltaic cell, and the potential difference between the electrodes is measured. On

the other hand, the electrical circuit may be arranged to produce a current flow through the fluid in the well and between the electrodes, thus measuring the resistance or conductance of the fluid; After the initial test is made fluid is then caused to flow into the well from the surrounding formation such as by lowering the head of oil by. the bailing process. After this step the testing process is repeated and a record made. Where water has entered the well, the electro-.

chemical qualities will be diflerent from those of the dormant fluid in the well, and this will be clearly visible on the recording instrument or on the records which are made. Where this difference in electrical characteristics occurs which may be greater current flow, less current flow,

greater voltage, or less voltage, the water has entered the well and by cementing at this point may be excluded therefrom. In the alternative process of my invention no test is made prior to the bailing step, but the first step in the process is to bail ofi the material in the well so as to cause an ingress of fluid. A test is then made, as pointed out heretofore. Thereafter'an additional bailing operation may be performed to cause an ingress of additional live fluid. Another test is then made and the records obtained from the two tests are compared, and where the diiierences in electro-chemical characteristics occur, this is the point of entrance of fluid into the well.

I have further discovered that where there is a water leakage into a well the electro-chemical characteristics of the fluid or material in the well adjacent this point where the water leakage exists are difierent from the electro-chemical char- I acteristics of other material in the well which has been allowed to age or become dormant. By the use of my invention itis possible to locate the leakage point without causing live fluid to flow into the well; and it is therefore an object of my invention to provide a method of locating waterleakages in which it is unnecessary to place any special materials, such as electrolytes, in the well, and in which a bailing step is unnecessary. One explanation of this condition is that water is a better conductor of heat than oil, and therefore the formation temperature is better transmitted to the well. The heat of the water formation therefore is transmitted or radiated to the material in the well which lies immediately adjacent the water bearing formation, and this difference in temperature is suificient to produce small electro-chemical difierences between this material lying adjacent the water bearing forma tion and material in other parts of the well.

The method of my invention in its preferred form depends on the measurement or indication of microvolts or microamperes, and it is therefore very necessary to maintain uniform or con- -stant the various factors which afiect the method so that the only variable value in the circuit which I employ is caused by the differences in the electrochemical characteristics of the material or fluid in the well. I have found it to be quite essential to maintain a uniform relationship between electrodes which I employ in my process and which I lower into the well in order to determine the eleetro-chemical characteristics of the material or fluid in the well, and the wall of the well. I find -it highly desirable to cause the electrodes to accurately follow the contour of the well in order that conditions and relationships may be maintained constant. If the electrodes do not have a uniform position with respect' to the axis of the well potential diiferences .between the electrodes in the wall of the well will change and electrical or electro-chemical leakages will occur to different extents, which naturally affect the values of the readings obtained at the surface of the ground, with the result that deviations in the readings are produced by causes other than electro-chemical qualities or characteristics 'of the fluid in the well. It is accordingly an object of my invention to provide a method of locating water leakages in a well in which movable electrode means employed in the process is maintained in a uniform relationship to the axis or contour of the wellwhen it is moved into various positions along the well.

A further object of my invention is to provide a method of the character pointed out in which the pair of electrodes is maintained substantially concentric to and in alignment with the axis of the well for all positions into which the electrodes are moved along the well.

The term electro-chemical" as employed throughout this specification is intended to include both the electrical action or reaction which results from the forming of a voltaic cell in the material or well fluid or from the passageof an electric current through or the impressing of a potential difference on the well fluid.

My invention may be applied to wells which are being pumped, to wells which are filled with mud and are not flowing, and,also to wells which flow by reason of subterranean pressures. In the latter case the 'well is first capped and thereafter the test of my invention is made.

Other objects and advantages of my invention will be pointed out in the course of the following detailed description of various forms in which I have practiced my invention. It should be understood, however, that various modifications and alterations may be made without departing from the spirit and scope of my invention, that the detailed description is intended to instruct those skilled in the art as to the manner in which my invention may'be practiced, and that in view of these facts I do not wish or intend that-my invention be limited to the precise details described herein, but wish my invention to be construed in accordance with the scope of the appended claims. I

Referring to the accompanying drawings which diagrammatically illustrate apparatus capable of performing the methods of my invention:

Fig. 1 is a diagrammatic view illustrating my apparatus in use in a well. Fig. 2 is a diagrammatic view of a graph, chart, or curve made by the recording instrument employed asa part of the apparatus shown in Fig. 1, which curve was made from a test of the wall material prior to the bailing process and prior to the entrance of live fluid into the well.

Fig. 3 is a view similar to Fig. 2 showing the curve obtained in a test of the electro-chemieal qualities of the contents of .the well after live fluid has been caused to enter the well.

Fig. '4 is a view similar to Fig. 1 showing an alternative form of apparatus.

Fig. 5 is a vertical sectional view illustrating a form of electrode construction which I may employ in my invention. 1

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 5.

Referring to the drawings in detail, and particularly Fig. 1, the numeral ll represents a well in which a well casing 12 has been installed. The

lower end of the well casing 12 has been cemented at H to a shale IS in order to seal from the well all formations above the shale l5. At the lower part of the well II and below the shale I5 are sand formations I6, I! and I8 which are separated by shales' l9 and 20. For the purpose of illustrating the invention, it will be assumed that its own level, as indicated at 2|.

remove the pumping apparatus .from the well and to thereafter allow the fluidin the well to seek When this is done the additional steps of the process of my invention may be performed by the apparatus which I will now describe. The numeral 25 represents a flexible cable which extends over a sheave i 28 from a drum 21 on which this cable may be wound. The cable "includes a pair of conductors 23 and 30. The ends of these conductors.

29 and 30 are connected to electrodes 3| and 32.

. In the form of apparatus illustrated in Fig. 1

these-two electrodes and the fluid in the well constitute a voltaic cell, and therefore these elec trodes 3| and 32 in reality constitute the plates of a one-cell battery. It is desirable to use different metals for these plates which are electrochemically opposite to each other, such, for example, as cadmium and antimony.

At the surface of the ground the conductors 29 and 30 are connected to a recording device 34 which is designed to record the potential difference between the electrodes 3| and 32 or the changes in potential difference between these two electrodes at different positions in the well. As

pointed out heretofore, it is necessary to use an extremely sensitive recording device, and the one illustrated herein is a microvoltmeter adapted to record from zero to one hundred microvolts. In the practice of my invention, by use of a potentiometer circuit I balance the recording needle 35 to a central position on the scale 38 so that a difference in electro-potential between the electrodes 3| and 32 in either direction, that is, in

increase or decrease, may be recorded on the recording device 34. The potentiometer circuit employs an adjustable rheostat, including a resistance 31 and an adjustable contact 38, one end of the resistance 31 being connected to the conductor 38, and the other end being connected to a source of energy, such as a battery 39. The adjustable contact 38 is connected to the recording device 34 and is adjustable in order to vary the resistance in the circuits. The battery 39 is connected through a potentiometer circuit conductor 4| to the conductor 29 as indicated at 42, and includes a rheostat in.the form of a resistance 43 and an adjustable contact.

The recording meter 34 is only diagrammatically illustrated ,as are the other parts of the apparatus of my invention, and this recording meter may be any well known type which.'vvill automatically produce a chart of the current flows or voltages, such as is shown in Fig. 2. Likewise,

the recording device may be merely a meter which is observed by the operator and the different indications written down, from which a chart, graph, or curve .may be plotted.

The electrode apparatus which I prefer to. use is illustrated in Figs. 5 and 6. The cable 25 is secured by a connection 18 to an electrode'apparatus which supports the electrodes 3| and 32. This apparatus includes an upper shaft 1| and a lower shaft 12, the upper shaft having sup- 'ing which may. be installed in the well.

engagement with the wall of the well or the. cas- These at their central portions, as shown in Fig. 5, for

centralizing arms 83 are resilient so that they may accommodate themselves to different diameters of wells. The springs 88 and 8| always hold the central portions of the centralizing arms 83 outwardly so that the wall of the well will be engaged.

As is illustrated best in Fig. 5, the axis of the well is indicated by the point 84. The centralizing arms 83, being caused to engage the wall of the well, always maintain the electrodes -3i and 32 in a predetermined position with respect to the axis of the well. The distance A and the distance B which represent the distances betweenthe electrode 3| and the wall of the well and the electrode 32 and the wall of the well are always maintained uniform and of the same length. Where the diameter of the well is smaller the distances A and B will, of course, be smaller, and where the diameter of the well is larger the distances A and B-will, of course, be larger.

However, in a well of a given size these distances -A and B are maintained substantially uniform,

with the result that the electrical or electrochemical relationship between these electrodes and the wall of the well will be maintainedconstant or uniform, and there will be no deviating or changing influence on the recordings obtained at the surface of the ground due to any changes in value other than that produced by the electrochemical qualities of the material or fluid in the well. The electrode apparatus is so designed that the electrodes 3| and 32 are accurately guided along the axis of the well as the apparatus is moved either upward or downward in the well, and therefore the electrodes are caused to follow the contour of the well even though it deviates considerably from vertical, and in this way the relationship between the electrodes in the well is maintained sothat there will be no fluctuations which would cause false indications of the recording apparatus.

Having described the apparatus, 1 will now explain the method of my invention which is practiced by this apparatus. As pointed out heretofore, if the well'is'one which is being pumped the pump is removed and the oil allowed to seek its own' level or natural head. The first step in the process is to allow the well to stand for a sufflcient period of time to allow the fluid in the well to become dormant. The term dormant, it

will be understood, is merely a relative term and signifies that the fluid or material in the well has stood for a sufllcient length of time so that the electro-chemical qualities of the fluid are different from those of the live fluid which enters 1 the well during the bailing process, as will be explained shortly. The period of time which the contents of the well requires to become dormant may change in different wells, but in practice I usually allow the well to set from two to three hours. When the well has set for this period of time and the fluid. has become dormant, I then perform a test of the electro-chemical qualities of the contents of the well. This is done in the following manner. The electrodes 3| and 32 are lowered into the well, and when these electrodes enter theliquid an electro-potential difference isset up between these electrodes 3| and 32 and the needle 35 is deflected. I then adjust the pointers 38 and 44 of the rheostats in order that the potentiometer circuit will balance the current flowsin the circuit comprising the conductors 29 and 30 and will bring the needle 35 to a substantially central position on the scale 36. The electrodes 3| and 32 are then slowly lowered into the well and the deflections of the needle 35 observed, or if the recording device is one which produces a chart or curve, the curve is produced in accordance with that illustrated in Fig. 2.

As explained heretofore, the electrodes are caused to follow the contour or axis of the well and are maintained predetermined distances A and B from the wall of the well. In this way the only change in value in the performance of the method of my invention is that which is caused by changes in electrical or electro-chemical characteristics of the material or fluid in the well.

Referring to Fig. 2, the horizontal lines represent the depth of the electrodes 3| and 32 in feet, the first heavy line being 4300 feet, the second heavy line being 4400 feet, and the intermediate light lines representing 10 feet each.. The vertical lines are merely arbitrary and for the pur-' pose of reference, since in my process the amount of deflection of the needle 35 or the difference in electro-potential or the current flow is immaterial except insofar as the electro-chemical characteristics or qualities recorded in the two tests are concerned when comparison is made, as will be explained shortly. Usually the curve produced from the original test is substantially as shown by the curve 58 in Fig. 2 and fluctuates on either side of the zero positions on the chart, it being understood that the zero position is merely the central position of the needle 35 on the scale 35, to which position it is adjusted by adjust ing the resistance in the circuits, as pointed out heretofore.

The apparatus is then removed from the well, the graph removed from the recording apparatus, and a new piece of graph paper installed, or turned back and different color ink used for next curve. live fluid is then caused to enter the well by lowering the liquid head in the well. This is conveniently done by a bailing process. The well then seeks its own level and in sodoing live fluid will flow into the well. In this instance water will flow from the formation i! into the well H. A second test of the electro-chemical qualities of the contents of the well is then made in accordance with the previous test without, however, changing the set-up of the apparatus, and a curve or chart as shown in Fig. 3 is made. Where live fluid has entered the well the curve 5') and the curve 5! shown in Fig. 3 will be different, since the electro-chemical qualities of the live fluid are different from those of the dormant material in the well, which difierences are very small but are recorded on the microrecording means 35. As illustrated in Fig. 3, the curve 5i has a peak 52 which is not present in the curve 50, and therefore the point of entrance of water into the well is as shown on the chart of Fig. 3 at approximately 4520 feet. If it is desired to have additional corroboration of the point of entrance 'of water of the bailing process, testing may be repeated and the peak will be increased as'indicated by dotted lines 53. With the information given by the charts shown in Figs. 2 and 3 and the curves 50 and 5! thereof, the water sand I! may be sealed from the well. Thereafter water will not In the method of my invention which does not involve the bailing step I follow the same practice in allowing the fluid or material in the well to become dormant, and therefore the electrochemical characteristics thereof are different from the live fluid-in the formation. As pointed out heretofore, a difference in temperature will produce a difference in the electro-chemical qualities of the fluid or material in the well. At those ture of the material in the well adjacent the water bearing formation will be raised by heat transmission to approximate 179? F. There will, therefore, be a slight difference in the electro-chemical qualities of the fluid in the well adjacent the water bearing formation and other. fluid in the well. Although this difference may be slight. it is possible to record it by the use of a microammeter or a microvoltmeter.

In the form of my invention illustrated in Fig. 4

various parts may be the same as illustrated in Fig. 1 except that in Fig. 4 the apparatus measures the resistance or conductance of the contents of the well rather than the potential difference between the electrodes 3| and 32, and the electrodes 31 and 32 need not be made from dissimilar metals. The only difference in the electrical hook-up is the use of a battery 60 in the conductor 30, and when used the potentiometer circuit is used to balance the current flow so that the recording needle 35 will occupy a central position on the scale 35. When the electrodes 3i and 32 are lowered into the well the changes in resistance or conductance of the well contents between these two electrodes change in accordance with the electro-chemical characteristics or qualities of the material, and since this material forms a part of the electrical circuit these differences will be recorded on the recording means 34. In the performance of the process the various steps which are performed may be the same as the method explained in connection with Fig. 1 except that the curves produced will not be the potential differences or current flow produced by the voltaic cell, but .will be the difference in resistance of the material at various points. The live fluid, having difierent electro-chemical qualities from the dormant fluid in the well, will have a different resistance or conductance, and therefore the point of entrance of water into the well may be located.

As pointed out heretofore, a further form of my method does not require the performance of a test before bailing and maybe practiced by first allowing the 'fiuid to become dormant, then bailing liquid from the well in order to cause an ingress of live fluid, and then the making of a test, as pointed out heretofore. The first test will produce a curve somewhat as illustrated in Fig. 3 including a peak 52. After this test is made the Well is then again bailed and another test is made, and where the water has leaked into the well there will be a larger peak, such as indicated at 53 in Fig. 3, which in turn indicates the point of leakage into the well.

In the practice of my invention it is unnecessary to introduce special materials, such as electrotypes, into the well, but the fluid or material which has remained in the well from a previous operation may be used. By this I mean after the well has been placed on the pump the oil or emulsion which remains in the well when the pump is removed may be used. If the well is a entrance of said connat'e fluid.

. different levels in said well and making a record v 2,184,888 flowing well, this well may be capped and the material in the well may be employed. The process of my invention is a great saving'over the prior art not only so far as time is concerned, but also in expense. The depositing of electrobe reduced to one-half or one-third of the costwhere prior art methods are employed.

I believe my invention to be broadly new and based on .a discovery and" principle of operation totally different from the prior art, and I therefore wish my invention tobe broadly construed in accordance with the appended claims.

I claim as my invention: a

1. A method of locating the point of entrance of water into a well, which method includes the steps or: testing the electro-chemical 'qualities of the residual material in the well-at different levels in the well without the addition of any substance to the material in the well; causing an ingress of connate fluid into the well; and again testing-the electro-chemical qualities of the material in the well at diflerent levels to determine the-point of entrance of said connate fluid.

2. A method of locating'the point of entrance of water into a well, which, method includes the steps of: testing the electro-chemical qualities of tents of said well at different levels, and making a record thereof; and determining the point of entrance of said live fluid in said well by comparing said records.

6. A method of locating the point of entrance of water into a well, which method includes the steps of allowing the residual material in said well to become dormant; removing from the well a part of the material therein, thus causing live fluid to flow into said well; testing the electrochemical qualities of. the contents of the well at different levels and making a record thereof; again removing material from said well to cause additional live fluid to flow into said well; again testing the electro-chemical qualities of the contents cf said well at different levels, and making a record thereof; and determining the point of entrance of said live fluid in said well by comparing said records.

7. A method of locating the point of entrance of water into awell, which method includes the the residual material which has remained in the well from previous normal operationstherein at difierent levels in the well; causing an ingress of connate fluid into the well; and again testing the electro-chemical qualifies of the materialin the well at difierent levels to determine the point of 3. A method of locating the point of entrance of water into a well,- which method includes the steps of: allowing the residual. material in the well to become dormant; testing the electrochemical qualities of said dormant material at thereof; causing live fluid to.flow into said well; again testing the electro-chemical qualities of the contents of the well at different levels, and making a record thereof; and determining, by comparison of said records, the point of entry of fluid into said well.

4. A method of locating the point of entrance of water into a well, which method includes the steps of: allowing the residual material in the well to remain in said well for a 'sufficientlength comparison of said records, the point of entry of i 1 fluid into said well.

5. A method of locating the point of entrance of .water into a well, which method includes the steps of: removing from the well a part of the residual material which has remained therein from a previous normal drilling or production operation, and without the addition of any substance to the material in the well, thus causing live fluid to flow into said well; testing the electro-chemical qualities of the contents of the well at diiferent levels and making a record thereof;

again removing material from said well to cause additional live fluid to flow into said well; again testing the electro-chemical-qualities of the consteps of: allowing the residual material in said .well to become dormant; testing the electrochemical qualities of the contents of'the well at different levels and making a record thereof; again removing material from said well to cause additional live fluid to flow into said well; again testing the electro-chemical qualities of the contents of said well at different levels, and making a record thereof; and determining the point of entrance of said live fluid in said wellby comparing said records. 1

8. A method of locating the point of entrance of water into a well, which method includes the steps of: allowing the residual material in the well to become dormant; lowering a pair of electrodes of dissimilar metal into said well to form a voltaic cell consisting of said electrodes and the material in said well adjacent said electrodes; maintaining a uniform relationship be- .tween the wall of said well and said electrodes; and measuring the electrical characteristics produced by said voltaic cell.

9. A method of locating the point of entrance of water into a well, which method includes the steps of: allowing the residual material in the well to remain in said well for a suflicient length of time for the electro-chemical qualities to change and for the adjacent water bearing formation to affect the electro-chemical qualities of the material in said well adjacent to said water bearing formation; lowering a pair of electrodes of dissimilar metal into said well to form a voltaic cell consisting of said electrodes and the material in said well adjacent said electrodes; maintaining a uniform relationship between the '1 wall of said well and said electrodes; and measuring the electrical characteristics produced by said voltaic cell.

10. A method of locating the point of entrance of water into a well, which method includes the steps of: allowing the residual material in the well' to become dormant; lowering a pair of spaced electrodes into said well; maintaining a uniform relationship between the wall of said well and said electrodes; and measuring the electrical charatceristics of the material between said electrodes.

11. A method of locating the point of entrance of water into a well, which method includes the steps -of: allowing the residual material in the well to remain in said well for a suflicient length of time for the electro-chemical qualities to change and for the adjacent water bearing for- .mation to affect the electro-chemical qualities of the materialin said well adjacent to said water bearing formation; lowering a pair of spacedelectrodes into said well; maintaining a uniform relationship between the wall of said well and said electrodes; and measuring the electrical characteristics of the material between said electrodes.

12. A method of locating the point of entrance 'of water into a well, which method includes the steps of: allowing the residual material in the well to become dormant; lowering a pair of electrodes of metal into said well and to form a voltaic cell consisting of said electrodes and the material in said well adjacent said electrodes; causing said electrodes to follow the contour of said well when the same are lowered in order to maintain a uniform relationship between the wall of said well and said electrodes; and measuring the electrical characteristics produced by said voltaic cell.

13. A method of locating the point of entrance of water into a well, which method includes the steps of: allowing the residual material in the well to remain in said well for a sufllcient length of time for the electro-chemical qualities to change and for the adjacent .water bearing formation to afiect the electro-chemical qualities of the mate-- teristics produced by said voltaic cell.

14. A method of locating the point of entrance of water into a well, which method includes the steps of allowing the residual material in the well to become dormant; lowering a pair of spaced electrodes into said well; causing said electrodes to follow the contour of said well when the same are lowered in order to maintain a uniform relationfluid into a well, comprising: discontinuing norship between the wall of said well and said electrodes; and measuring theelectrical characteristics of the material between said electrodes.

15. A method of locating the point of entry of fluid into a well, comprisingz'discontinuing normal operations in the well; making a flrst observation of the status of consecutive points in the content of a well in static condition without adding sub-- stance to the content of the well from the surface; changing said status by causing a flow of fluid into the well from the formation'in which the well is formed; making a second observation of the status of consecutive points in'the content of the well; and determining the location of the point of entry of said fluid into the well by comparing said 1 second observation with said flrst observation and noting where the status of content of the well has been changed by said entry of fluid.

16. A method for locating the point of entry of mal operations in the well and then making consecutive tests of the electro-chemical qualities of the fluid remaining in the well without placing of any substance in the well from the surface, said tests including a step of causing entry of fluid into the well from the adjacent formation preceded and followed by tests of the electro-chemical qualities of the fluid in the well, and comparing said tests.

17. A method for locating the point of entry of fluid into a well in which drilling operations in the presence of mud have been carried on, comprising: discontinuingv the normal operations in the well and then making consecutive tests of 'the. electrochemical qualities of the fluid comprising 1 mud remaining in the well without the placing of any substance in the well from the surface, said tests including a step of causing entry of fluid into the well from the adjacent formation preceded and followed by tests of the electro-chemical 4 qualities of the fluid and mud in thewell, and comparing said tests.

GEORGE E sums.

CERTIFICATE OF CORRECTION. Patent No. 313L5 8. December 26, 19 9.

. GEORGE E. ENNIS. I It is her eby ertified that error appears in the printed specificatiori v of the above numberegi patent requiring correction as follows: Page 1', sec- 0nd column, line 7, for "he" read. the; page 2, secondcolumn', lihe b7, f0: the word "wall" read well; and the said Letters Patent should be read with this cori-ection' therein that the some may conform to the r eeord of the case in the Patent Office. 4

Signed and sealed this 20th day 'of Februery; A, 1). 191p.

A Henry Vim Arsdale, Acting Qonmlissionep of Patents. 

